Systems, devices, and methods for splitter optics in wearable heads-up displays

• US 9,958,682 B1
• Filed: 05/05/2016
• Issued: 05/01/2018
• Est. Priority Date: 02/17/2015
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Thalmic Labs Inc.
• Inventors: Moore, Joshua, Holland, Lloyd Frederick
• Primary Examiner(s): Chwasz, Jade R
• Application Number:
  US15/147,638
• Time in Patent Office: 726 Days
• Field of Search: 359 9, 359 10, 359 11, 359 21, 359 22, 359 29, 359 35
• CPC Class Codes: G02B 2027/0125 Field-of-view increase by wavefront division
• CPC Class Codes: G02B 2027/0174 holographic
• CPC Class Codes: G02B 2027/0178 Eyeglass type eyeglass details G02C
• CPC Class Codes: G02B 27/0172 characterised by optical features
• CPC Class Codes: G02B 27/12 operating by refraction only

Abstract

Systems, devices, and methods for optical splitters are described. An optical splitter includes a transparent polygonal structure having an input side to receive light from a light source and an output side that is segmented into multiple facets. Each facet is engineered to provide a respective planar surface that is oriented at a different angle in each of at least two spatial dimensions relative to the other facets in order to refract and route a respective portion of the light along a respective set of optical paths. The input side may be faceted as well to further refine the optical paths. A particular application of the polygonal structure in an optical splitter providing eyebox expansion by exit pupil replication in a scanning laser-based wearable heads-up display is described in detail.

Claims

1. A wearable heads-up display (“

WHUD”

) comprising;

a support structure that in use is worn on a head of a user;

a scanning laser projector carried by the support structure;

a holographic combiner carried by the support structure, wherein the holographic combiner is positioned within a field of view of an eye of the user when the support structure is worn on the head of the user; and

an optical splitter carried by the support structure and positioned in an optical path between the scanning laser projector and the holographic combiner, wherein the optical splitter includes a transparent polygonal structure that comprises;

an input side oriented to receive laser light from the scanning laser projector and in-couple the laser light into a volume of the optical splitter; and

an output side having N=4 facets, each of the N=4 facets oriented to out-couple a respective portion of the laser light from the volume of the optical splitter and direct the respective portion of the laser light along a respective optical path towards the holographic combiner, wherein;

the N=4 facets are arranged in a two-by-two array with each one of the N=4 facets sharing a first edge with a first other one of the N=4 facets and a second edge with a second other one of the N=4 facets,

each one of the N=4 facets comprises a respective rectangular surface oriented at a different angle in three-dimensional space relative to the other ones of the N=4 facets,

each one of the N=4 facets is oriented to at least partially face away from each of the other ones of the N=4 facets, and

a respective first vertex of each one of the N=4 facets mates with the respective first vertices of each of the other ones of the N=4 facets to form a vertex on a convex outer surface of the output side of the optical splitter, and wherein;

the holographic combiner comprises at least one hologram positioned and oriented to receive the respective portions of the laser light from the N=4 facets of the optical splitter and redirect each respective portion of the laser light towards a respective one of N exit pupils at the eye of the user.

2. The WHUD of claim 1 wherein each of the N=4 facets of the output side of the optical splitter is oriented to direct a respective portion of the laser light from the scanning laser projector along a respective optical path towards the holographic combiner effectively from a different respective one of N spatially-separated virtual positions for the scanning laser projector.

3. The WHUD of claim 1 wherein each of the N=4 facets of the output side of the optical splitter comprises a respective planar surface, and wherein the planar surface of each one of the N=4 facets of the output side of the optical splitter is oriented at a different angle in each of at least two spatial dimensions relative to the other ones of the N=4 facets of the output side of the optical splitter.

4. The WHUD of claim 3 wherein the planar surface of each one of the N=4 facets of the output side of the optical splitter is oriented in a respective plane that intersects each of the respective planes of the other ones of the N=4 facets along a respective line of intersection, and wherein no line of intersection between the respective planes of any pair of facets among the N=4 facets is parallel to any other line of intersection between the respective planes of any other pair of facets among the N=4 facets.

5. The WHUD of claim 1 wherein the input side of the optical splitter includes at least M facets, where M is an integer greater than 1, each of the M facets oriented to in-couple a respective portion of the laser light from scanning laser projector into the volume of the optical splitter and direct the respective portion of the laser light towards a respective subset of P of the N=4 facets on the output side of the optical splitter, where P is an integer less than or equal to N.

6. The WHUD of claim 5 wherein the number N=4 of facets on the output side of the optical splitter is greater than the number M of facets on the input side of the optical splitter and P is less than N.

7. The WHUD of claim 5 wherein the input side of the optical splitter includes M=2 facets, and wherein a first edge of a first one of the M=2 facets mates with a first edge of a second one of the M=2 facets and the first facet and the second facet are oriented to at least partially face one another and form an obtuse angle on a concave outer surface of the input side of the optical splitter.

8. The WHUD of claim 5 wherein each of the M facets of the input side of the optical splitter comprises a respective planar surface, and wherein the planar surface of each one of the M facets of the input side of the optical splitter is oriented at a different angle in at least one spatial dimension relative to the other ones of the M facets of the input side of the optical splitter and relative to each of the N=4 facets of the output side of the optical splitter.

9. The WHUD of claim 1 wherein the optical splitter comprises multiple separate pieces that are bonded together.

10. An optical splitter including a transparent polygonal structure that comprises:

an input side oriented to receive light from a light source and in-couple the light into a volume of the optical splitter; and

an output side having N=4 facets, each of the N=4 facets oriented to out-couple a respective portion of the light from the volume of the optical splitter and direct the respective portion of the light away from the optical splitter along a different respective optical path, wherein the N=4 facets are arranged in a two-by-two array with;

each one of the N=4 facets sharing a first edge with a first other one of the N=4 facets and a second edge with a second other one of the N=4 facets, and

a respective first vertex of each one of the N=4 facets mating with the respective first vertices of each of the other ones of the N=4 facets to form a vertex on a convex outer surface of the output side, and wherein each of the N=4 facets comprises a respective rectangular planar surface that is oriented;

at a different angle in three-dimensional space relative to the respective rectangular planar surfaces of the other ones of the N=4 facets;

to at least partially face away from each of the other ones of the N=4 facets; and

in a respective plane that intersects each of the respective planes of the other ones of the N=4 facets along a respective line of intersection, wherein no line of intersection between the respective planes of any pair of facets among the N=4 facets is parallel to any other line of intersection between the respective planes of any other pair of facets among the N=4 facets.

11. The optical splitter of claim 10 wherein the input side includes at least M facets, where M is an integer greater than 1, each of the M facets oriented to in-couple a respective portion of the light from the light source into the volume of the optical splitter and direct the respective portion of the light towards a respective subset of P of the N=4 facets on the output side, where P is an integer less than or equal to N.

12. The optical splitter of claim 11 wherein the number N=4 of facets on the output side is greater than the number M of facets on the input side and P is less than N.

13. The optical splitter of claim 11 wherein the input side includes M=2 facets, and wherein a first edge of a first one of the M=2 facets mates with a first edge of a second one of the M=2 facets and the first one of the M facets and the second one of the M facets are oriented to at least partially face one another and form an obtuse angle on a concave outer surface of the input side.

14. The optical splitter of claim 11 wherein each of the M facets of the input side comprises a respective planar surface, and wherein the planar surface of each one of the M facets of the input side is oriented at a different angle in at least one spatial dimension relative to the other ones of the M facets of the input side and relative to each of the N=4 facets of the output side.

15. The optical splitter of claim 10 wherein the transparent polygonal structure comprises multiple separate pieces that are bonded together.